To visit "The Radical Camera: New York's Photo League, 1936-1951" at the Contemporary Jewish Museum is to look backward from the surveillance age to the age of the camera as significant social witness.

Today, we feel merely small shocks when a citizen with a smartphone captures police brutality or the loutish sincerity of a candidate for high office.

But the camera workers of the Photo League - a large, loose and contentious association formed in the 1930s - turned their lenses on a world whose injustices had until then gone little challenged in America by documentary.

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The picture press, especially weekly magazines, where some Photo League members' work appeared, occasionally led or reinforced slow rises in popular sentiment against economic and discriminatory injustice.

The survey's bracket dates - 1936 to 1951 - hint at the shifting social and ideological background of the Photo League's turbulent life span. It coalesced during the Great Depression, registered the Second World War's seismic jolts to American life and was hounded out of existence by the anticommunist hysteria of the early Cold War years.

But even setting aside the urgent historical background, "The Radical Camera" offers a stirring array of viewpoints on picturable reality and photographers' duties to it and to their medium.

Newman's "Halloween, South Side" (1951) shows four children - two black, one white, a fourth strapping on a mask - their troubled expressions a touching pantomime of anxiety at the expectations pressing on them from beyond the frame.

Louis Stettner's "Coming to America" (1951) shows an immigrant parent and child shivering in deck chairs against a wind that tears at the sea around them. Stettner's image might serve as one of the exhibition's signatures, as Jewish and other waves of war-driven immigration inform the social landscape of the Photo League's era.

The proper balance of photographic values - formal, documentary, activist, autobiographical - was a source of lively dispute among Photo League members and exhibitors. (The league provided both instruction and exhibition opportunities to its members.)

Some, such as Consuelo Kanaga in her "Untitled (Tenements, New York)" (1937), combined formal power and documentary provocation. Others did the same while zeroing in on American contradictions unmasked by the Depression or manifest segregation.

The democratization of photographic activism began with the new availability of 35mm camera equipment on which Photo League practitioners depended. That democratizing drift, accelerated by more recent technical innovations, has led to a trivialization of camera work in our time. "The Radical Camera" delivers a stinging sense of what we have lost as a consequence, and of what social maladies persist into our own day.

Mark's "Circus": In the early 1980s, American photographer Mary Ellen Mark began studying circuses in India, producing the classic album of images "Indian Circus" in 1993.

The Jenkins Johnson Gallery presents a large selection of platinum prints from the series in a show that ends Saturday.

"When I photographed the circuses in India," Mark wrote in the book, "all of my senses were keenly alerted. I have such strong memories of the wonderful sounds, often Western popular music played on a worn saxophone and old drums, interspersed with lion roars and bells announcing acts. I think about the pungent smell of tiger urine and the exotic perfume of burning incense tinged with jasmine floating from every tent's tiny homemade temple shrine. I also recall extraordinary conversations, the laughter of the child performers, and the shouts of fighting clowns."

Although her photographs capture mere shadows of the experience she describes, they powerfully evoke roving, informal, often family-based institutions doggedly wringing a livelihood from performances that tested their limits of physical endurance and their tolerance of one another. The stresses they record make Mark's "Acrobat Sleeping, Famous Circus, Calcutta" (1989) one of the most affecting, though least bizarre, images in the series.

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